Finished a mono pair F3 clones…
Thanks to Mr. Pass and the solid contributions here in the forum!
These amps sound sweet[emoji445][emoji106]
Hi Ben & Jeff,
Thanks for your advice.
I planned to use the external bridge rectifier, is this one good enough?
GBPC3506 ON Semiconductor / Fairchild | Mouser
Thanks for your advice.
I planned to use the external bridge rectifier, is this one good enough?
GBPC3506 ON Semiconductor / Fairchild | Mouser
That rectifier will do nicely.
You can use "Fast Recovery" type rectifiers, but generally they don't come in a bridge package. They will reduce ringing in the transformer. You can also use Quasimodo to pick a RC snubber network that will do the same. Neither are necessary; both are possibly of benefit.
You can use "Fast Recovery" type rectifiers, but generally they don't come in a bridge package. They will reduce ringing in the transformer. You can also use Quasimodo to pick a RC snubber network that will do the same. Neither are necessary; both are possibly of benefit.
I got my F3 up and running. It is a Rawson build that I saw on audio mart at a nice price. Having updated a pile of rawsons last year, I thought I’d try this F3. I added grounding - it was totally absent. Classic rawson. It looks like the F1 psu, or Jeff’s up above. 2 single rails, each rail with a cl60 to chassis. And I have the mains ground to chassis, that was missing, too. I added snubbers and a power LED. Blue, of course. It sings on the test bench.
No other mods yet. All caps are original. Perhaps I’ll go for enhancements in the future.
I’ll try it on my horns this week. How will it compare to the mighty SissySIT?
No other mods yet. All caps are original. Perhaps I’ll go for enhancements in the future.
I’ll try it on my horns this week. How will it compare to the mighty SissySIT?
Attachments
nice amp per se
of course, Blue Led being a necessity, Papa's secret ingredient
to relieve more of secrets - one channel must have Blue LED powered from positive rail, while second channel must have Blue LED powered from negative rail
when having single rail supply, just one channel's LED is allowed
............same breed as Sissy, but Sissy being more equal animal
of course, Blue Led being a necessity, Papa's secret ingredient
to relieve more of secrets - one channel must have Blue LED powered from positive rail, while second channel must have Blue LED powered from negative rail
when having single rail supply, just one channel's LED is allowed
............same breed as Sissy, but Sissy being more equal animal
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Thank you guys [emoji106]
It was a fun project with a lot to learn about the LU JFet and the triode cell. Meanwhile the amps received an update.
View attachment 1
If anyone wondered, the BNC connector is directly wired to the amplifiers output to drive the F4 that is coming [emoji3060]
It was a fun project with a lot to learn about the LU JFet and the triode cell. Meanwhile the amps received an update.
View attachment 1
If anyone wondered, the BNC connector is directly wired to the amplifiers output to drive the F4 that is coming [emoji3060]
Wonderful build Joschl. Congratulations!
How large are those heatsinks? Do you have a part number for that?
Thanks,
Dennis
How large are those heatsinks? Do you have a part number for that?
Thanks,
Dennis
Thanks for the info.
I have some 11" x 11" heat sinks from R-theta from way back when,
but yours look much cooler.
I have some 11" x 11" heat sinks from R-theta from way back when,
but yours look much cooler.
Thanks. I liked the shape with the lower fins at the end. I have six of them in total. So F3, F4 and one tbd…
nice amp per se
of course, Blue Led being a necessity, Papa's secret ingredient
to relieve more of secrets - one channel must have Blue LED powered from positive rail, while second channel must have Blue LED powered from negative rail
when having single rail supply, just one channel's LED is allowed
............same breed as Sissy, but Sissy being more equal animal
Hi,
May I know why the LED needed to be blue and not RED, GREEEN etc...
And why only one channel if for single rail?
At risk of publicly confirming a nearly complete lack of knowledge, let me try to expand on ZM’s succinct (but I think lighthearted) notes.
The LED can be any colour - blue is a kind of signature for some Pass amps, so maybe the builder intended it as a bit of an hommage to NP. Or maybe blue is a favourite colour - who knows?
One thing about blue LED’s though, they can be noisy, relative to other colours. For a single LED one could opt to move the tap to a reservoir capacitor in the power supply board where any injected noise can be dealt with a bit better.
The LED can be any colour - blue is a kind of signature for some Pass amps, so maybe the builder intended it as a bit of an hommage to NP. Or maybe blue is a favourite colour - who knows?
One thing about blue LED’s though, they can be noisy, relative to other colours. For a single LED one could opt to move the tap to a reservoir capacitor in the power supply board where any injected noise can be dealt with a bit better.
now seriously- that LED part of my post - 158% joking
regarding LED noise - in 99.9% of cases, that's Audiophoolery
any power amp is hardly possible to even get a mile near to remaining 0.1% of cases
regarding LED noise - in 99.9% of cases, that's Audiophoolery
any power amp is hardly possible to even get a mile near to remaining 0.1% of cases
I finally pulled my SissySIT out and replaced with F3 on my main system. The amp serves 500Hz to 20kHz in an active horn rig. I adjusted for gain difference and sat back to enjoy.
ZenMod - You're right about being similar breed to SissySIT. F3 is indeed a very nice sounding amp. It will take some very critical listening to make detailed notes to compare the 2 amps. In the first little while listening I can say the F3 shares many similar traits. Openness, immediacy, space, ease.
ZenMod - You're right about being similar breed to SissySIT. F3 is indeed a very nice sounding amp. It will take some very critical listening to make detailed notes to compare the 2 amps. In the first little while listening I can say the F3 shares many similar traits. Openness, immediacy, space, ease.